1. Field of the Invention
The present invention relates to a semiconductor device having a shield structure. More particularly, the present invention relates to a semiconductor device having an analog circuit section and a digital circuit section, and further having a shield structure for shielding the analog circuit section.
2. Description of the Related Art
As a semiconductor device suitable for high-density mounting, a WLP (Wafer Level Package) is known. A WLP is a semiconductor device obtained by forming bump electrodes for external connection on connection pads connected to the respective semiconductor integrated circuits on a wafer while the circuits are still on the wafer, filling a sealing agent between the bump electrodes, thereafter dicing the wafer. Each WLP has the same area as that of the semiconductor substrate obtained by dicing. Accordingly, even though each WLP is a packaged semiconductor device, the mounting density of the WLPs has been greatly improved. However, generally, in a case where the integrated circuits to be mounted are to be mounted with a super high density, it is difficult to use WLPs as such integrated circuits. This is because the pitch between the external connection electrodes becomes short. A semiconductor device described below, which is reduced in such difficulty, is now available. This semiconductor device is obtained by adhering each WLP on a base substrate having a larger area than that of the WLP, forming an insulating layer on the WLP and on the base substrate, forming a wire on the insulating layer so as to be connected to the electrode of the WLP, and forming an external connection electrode on the pad of the wire. If mounted on such a semiconductor device, the area of each WLP can be enlarged. Consequently, the pitch between the external connection electrodes can be increased, and the above-described difficulty can be reduced. Furthermore, a semiconductor layer in which a plurality of semiconductor devices form a stacked structure is now studied. Unexamined Japanese Patent Application KOKAI Publication No. 2005-142466 discloses a semiconductor device described below. This semiconductor device is obtained by placing a semiconductor component having a columnar electrode on its semiconductor substrate on a base plate having a larger plan-view size than that of the semiconductor component, forming an insulating layer on the base plate that appears around the semiconductor component, forming an upper insulation film on the semiconductor component and on the insulating layer, forming an upper wire on the upper insulation film so as to be connected to the columnar electrode of the semiconductor component, forming a solder ball on the connection pad portion of the upper wire, forming a lower wire under the base plate so as to be electrically connected to the upper wire through an upper and lower conducting portion, and mounting another semiconductor component under the connection pad portions of the lower wire.
Such a semiconductor device as described above has the following problem. In a case where a digital circuit section is constituted by a semiconductor component enclosed with an insulating member such as an insulating layer and an analog circuit section is constituted by another semiconductor component which is exposed to the outside, radiation noise from the digital circuit section interferes with the analog circuit section.